Almost 20% of the world population suffers from speech disorder, impairments and disabilities. In certain circumstances and due to illness, the larynx could be completely or partially removed. The larynx involves among other functions the production of sound in humans as it houses the vocal folds that are responsible for phonation. Injury or removal of the larynx will cause disorders or even loss of voice forever. Voice loss is likely to result in cases of laryngectomy or partial laryngectomy in which the larynx is entirely or completely removed, respectively. In such circumstances, one may no longer be able to force air from one's lungs through one's mouth to speak.
Some solutions that have been presented to address this problem include the use of an apparatus comprising a computer through which speech is synthesized. The user is able interact with the apparatus, either through writing and/or the use of the user's other senses to signal the apparatus for selecting characters on a list of ones displayed to the user by an automatic scrolling device on the user's computer screen. Such speech synthesizers include text prediction software as well as electronic voice synthesizers.
Other solutions have been presented in the field to tackle the issue of speech synthesis. For example, European Patent Application No. 92305078 discloses an external piezoelectric transducer which is able to detect voice sound vibration from the human head particularly the cheek and convert it into an electrical signal. This signal is then converted into speech (voice sounds). U.S. patent application Ser. No. 11/198,287 discloses a low power EM sensor capable of detecting tissue motion in the neck region, either from the sub-glottal (the section of the neck, where the neck meets the chest) and the supraglottal region (the section of the neck, where the neck meets the jaw). The signals detected through the EM sensor are synthesized into speech using a control algorithm. U.S. Pat. No. 5,888,187 describes the use of an implantable microphone, which may be piezoelectric crystal microphone, capable of generating electrical signals based on vibrations. The vibrations are picked up using a diaphragm. The electrical signal is further processed, filtered and converted into speech. German Patent Application No. 102009023924 discloses a system for sensing whisper/pseudo-whisper in the oral cavity of the human and converting it into an electrical signal. The signal is then processed, filtered and converted into speech (voice sounds) and/or written text. The system may be implantable or used as a releasable fixable prosthesis. U.S. patent application Ser. No. 13/118,285 discloses an intra-oral appliance for detecting tissue conducted vibrations generated by audible sounds from the oral cavity. The microphone employed in the appliance comprises a piezoelectric film present in vibration communication with the contact surface. The appliance is capable of wirelessly transmitting the signal containing user-generated sounds to a phone or radio. The publication Miyaoka et al. entitled “Applicability of piezoelectric sensors for speech rehabilitation”, published in the Journal of Medical Engineering & Technology, Vol. 33, No. 4, May 2009, pp. 328-333, discloses an external piezoelectric sensor capable of picking up signals during vocalizing tasks from the front of the neck for speech rehabilitation. All of the references described above are incorporated here by reference.
Examples of commercially available devices to assist individual's suffering from speech problems include communication display boards, electrolarynx, speech generating devices and voice amplifiers. Communication display boards consist of two types fixed (low-tech) and dynamic (high-tech) display boards. In a fixed board the symbols pictures, words and phrases are fixed whereas a dynamic display board has a touchscreen that is available to allow interaction by the user. The device is hand-held and the output voice of the dynamic board is a digitized sound from the speaker device. The digitized voice is generated from the device through non-vocal input by the user.
The Electrolarynx is another example of a hand-held device that helps people who lost their larynx/voice box. It is used to produce clearer speech to communicate and to increase/replace speech for people with sharp speech problems. With the improvement of digital and wireless technologies, additional devices are being offered in order to help such people to communicate more meaningfully and enjoy more in their daily lives. The Electrolarynx allows patients to speak long sentence that may be understood by others. Such devices need to be placed on the neck and turned on every time it is used. So, the use of the device requires the user to constantly hold it and press it against her or her nick. Furthermore, the speech tone generated by the electrolarynx sounds mechanical, which may be considered unnatural.
Speech-generating devices (SGD) are also known as voice output communication aids. SGD are electronic devices or software that allow a user who has speech damage the ability to select messages to be vocalized loud. The first type of these devices was a sip- and puff typewriter controller that was developed in the 1960s. Usually, when using the SGD, the output is slower than the actual speech.
A voice amplifier is a small portable device, which uses a speaker to offer clear and loud speech that is useful for people who have speech difficulties such as: vocal nodules, damaged or partially paralyzed vocal cords, impairment of throat or chest muscles or diminished lung capacity. The amplifier has a line input jack that may be connected to the output of a Speech Generating Device (SGD) to increase the loudness level of the user's voice in noisy surroundings and a high capacity rechargeable battery. Voice amplification offers many advantages for the user: it avoids damage or more damage for the throat, decreases misunderstandings & need for repetition, it offers easier, accurate communication and it is simple to use. Examples of voice amplifier devices are ADDvox™, BoomVox™, ChatterVox™, Oticon™, SoniVox™, Spokeman™, and Voicette™.
There is a desire in the field for the development of techniques to improve accuracy and/or quality of the synthesized speech in a cost efficient and durable fashion using easily accessible probing systems.